The brightness of the target area of the illumination should be appropriate. It should be pointed out that different eye conditions (such as general activities, bedside casual reading, writing and reading) have different requirements for brightness and uniformity of light, and there are detailed numerical values in the national standard . However, the type, power, and shape of the light source used in the desk lamp vary widely. The user must adjust the position and illumination angle of the light source according to the actual situation, so that the brightness of the target area meets the requirements of the national standard. Generally speaking, because the brightness of the visual light is subjective and the deviation is large, when adjusting the light, the brightness monitoring tool such as the eye-protection pen should be used . The safety of light for long-term, close-up use of the eye (such as reading / writing).